The present invention relates to a multichip configuration containing a multiplicity of semiconductor chips which are connected in parallel with one another in a module and whose control terminals are jointly connected, first, to an external driver circuit and, second, to a clamping device.
A multichip configuration containing semiconductor chips connected in parallel with one another in a module or in a wafer cell is known. Implemented in each of the semiconductor chips is, as an example of a power semiconductor component, an insulated gate bipolar transistor (IGBT). Instead of such an IGBT, another power semiconductor component can also be embodied, such as a MOS field effect power transistor, a thyristor or the like.
Gate terminals of the chips are combined at a point in the module, the point being connected to an external gate terminal of the module. The external gate terminal is therefore available externally to a user of the module.
In order then to avoid oscillations between the individual chips, there is between each gate terminal of the individual chips and the actual gate electrode of the IGBT a resistor. Therefore, between two gates of the chips, there is always a series circuit of two resistors. If, for example, the chips are considered, the series circuit contains the resistors, which are connected to each other via the gate terminal, the point and the gate terminal.
A user will connect the module gate terminal to an external driver stage that, inter alia, has a series circuit containing a first switch, a first resistor, a second resistor and a second switch between a positive voltage source and a negative voltage source. The gate terminal is in this case connected to the junction between the two resistors and can thereforexe2x80x94depending on the position of the switchesxe2x80x94have applied to it the potential from the positive voltage source, reduced by the voltage drop across the resistor, the potential of the negative voltage source, reduced by the voltage drop across the resistor, and a potential lying between the potential of the positive voltage source and the potential of the negative voltage source, corresponding to the resistor ratio of the resistors.
In addition, the module gate terminal is also connected to a clamping device, which has the task, in the event of a short circuit for example between an external collector terminal and an external emitter terminal of the module, as far as possible of preventing any rise in a gate voltage, that is to say the gate voltage of the chips. The external clamping device contains a series circuit of a zener diode with a capacitor between a fixed potential and a voltage source. A junction at the clamping voltage between the diode and the capacitor is connected to the module gate terminal via a clamping diode.
If a short circuit occurs on the output side of the module, then the voltage between the collector terminal and the emitter terminal rises. The voltage change effects a current flow (Miller current) through the Miller capacitors, as they are known. The current through the Miller capacitors must flow through the gate resistors before it can be dissipated into the large clamping capacitor through the clamping diode. Starting from the potential at the junction between the zener diode and the large clamping capacitor, the potential being kept approximately constant by the large clamping capacitor, irrespective of the level of the current through the Miller capacitors, there is further added the voltage drop across the clamping diode, which may be about 0.7 V, and the voltage drop across the internal gate resistors, which rises linearly with the Miller current caused by the Miller capacitors.
Attention then has to be paid to the fact that the actual gate voltage on the individual chips of the module cannot be measured directly in the module by a user. However, in the event of a short circuit, the short circuit current of the power semiconductor component, in the present example the respective IGBT, rises very sharply with the gate voltage.
The voltage drop across the internal gate resistors contributes to a not inconsiderable extent to the increased short circuit current and therefore to high loading on the power semiconductor component or the module, until the latter is destroyed.
The minimum level of the clamping voltage cannot be reduced further, since the power semiconductor component, in the normal conductive state, needs a minimum gate voltage of, for example, 15 V for good forward behavior.
It is accordingly an object of the invention to provide a multichip configuration that overcomes the above-mentioned disadvantages of the prior art devices of this general type, in which an increase in the short circuit current as a result of internal gate resistors is avoided.
With the foregoing and other objects in view there is provided, in accordance with the invention, a multichip configuration. The multichip configuration includes a module containing a gate/clamping terminal, a multiplicity of semiconductor chips connected in parallel and having a plurality of gate terminals and, a plurality of parallel circuits each having a resistor and a diode connected in parallel with one another forming a respective one of the parallel circuits. The parallel circuits each have a first side jointly connected to the gate/clamping terminal and a second side connected to one of the gate terminals. A driver circuit is connected to the gate/clamping terminal and a clamping circuit is connected to the gate/clamping terminal.
According to the invention, the object is achieved in a multichip configuration of the type mentioned at the beginning by the control terminals each being connected via a resistor to the driver circuit and each being connected via a diode to the clamping device. Given such wiring of the multichip configuration, internal gate resistors in the latter can be dispensed with, so that the voltage drop across these is minimized or can be neglected.
In a first advantageous development of the invention, provision is made for each semiconductor chip to be assigned one module gate terminal, and for the resistors and the diodes to be disposed outside the module.
A second advantageous development of the invention is distinguished by the fact that the module has a gate terminal and a clamping terminal, and in that within the module in each case the resistors of the semiconductor chip and the diodes of the semiconductor chip are jointly connected to the gate terminal and to the clamping terminal, respectively.
Finally, in a third advantageous development of the invention, provision is made for the module to have a gate and clamping terminal, within each semiconductor chip for the respective resistors and diodes to be connected in parallel with one another. The respective parallel circuits of the resistors and diodes of the individual semiconductor chips are connected jointly to the gate and clamping terminal.
In accordance with an added feature of the invention, the semiconductor chips each contains an insulated gated bipolar transistor, a MOS power transistor, a thyristor, or the like.
In accordance with an additional feature of the invention, the semiconductor chips contain a plurality of Miller capacitors.
In accordance with another feature of the invention, the resistor and/or the diode of the respective one of the parallel circuits is integrated on a respective one of the semiconductor chips.
In accordance with a further feature of the invention, the resistor and/or the diode of the respective one of the parallel circuit is implemented discretely from a respective one of the semiconductor chips.
In accordance with a concomitant feature of the invention, the driver circuit and the clamping circuit are an integrated single circuit.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a multichip configuration, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.